1. Field of the Invention
This invention relates to a multi-core optical fiber inspecting method and apparatus, and more particularly, to a multi-core optical fiber inspecting method and apparatus for confirming the coincidence between the alignment order of input-side cores of a multi-core optical fiber and the alignment order of output-side cores of the multi-core optical fiber for use as an optical communication medium, and for measuring a transmission loss of each core in one step.
2. Description of the Related Art
A multi-core optical fiber is prepared by aligning a plurality of optical fiber cores in the form of a tape in one plane. In the case of such a multi-core optical fiber, the alignment order of input-side cores is required to coincide with the alignment order of output-side cores Supposing that the alignment order of input-side cores is not coincident with the alignment order of output-side cores, it would be impossible to transmit optical signals to any target transmission line. However, the coincidence between the input and output core numbers needs confirming because nonconforming multi-core optical fibers in which the alignment order of input-side cores is not coincident with the alignment order of output-side cores are produced sometime during the process of manufacturing multi-core optical fibers.
In order to improve the production efficiency of multi-core optical fibers, moreover, it has also been required to measure the transmission loss of the optical fiber as its basic characteristic quickly without troublesome work.
A conventional method of verifying core numbers of multi-core optical fibers will be described with reference to FIG. 14 In FIG. 14, reference numeral 1100 denotes a light source; 1102, a multi-core optical fiber; and 1104, an optical power meter.
When core numbers of multi-core optical fibers are verified and when the transmission loss thereof is measured, the optical power meter 1104 has heretofore been used to measure output light from the emission end of each core of the multi-core optical fiber 1102 by putting the output of the light source 1100 into the incident end core of the multi-core optical fiber 1102. For example, the optical output of the light source 1100 is put into the incident end of No. 1 core, whereupon the optical power meter 1104 is used to verify the power of the optical signal that is output from the emission end of the No.1 core.
In the conventional methods of verifying core numbers of multi-core optical fibers, one output end of the multi-core optical fiber 1102 is split into single cores, which are separately connected to the optical power meter 1104 for measuring purposes. Consequently, much time has been required to take an accurate measurement as extremely complicated preparations for such the measurement are needed. Moreover, there has been the possibility of making errors in verifying core numbers because the optical output of each core is measured by switching the connections between the light source and the input-side cores.
An object of the present invention made under the circumstances stated above is to provide a multi-core optical fiber inspecting method and apparatus for confirming the coincidence between the alignment order of input-side cores of a multi-core optical fiber and the alignment order of output-side cores of the multi-core optical fiber and for measuring the transmission loss of the optical fiber as its basic characteristic simply, quickly and accurately in one step.
In order to accomplish the object above, according to a first aspect of the present invention, there is provided a multi-core optical fiber inspecting method comprising the steps of putting an optical signal into each incident end core of a multi-core optical fiber having a plurality of cores arranged in one plane, taking out the optical signal emitted from the emission end of the core in a time series mode according to the alignment order of emission-side cores of the multi-core optical fiber, and verifying core numbers of the respective cores of the optical fiber on the basis of the signal patterns thus taken out in the time series mode. Therefore, the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof can be confirmed simply, quickly and accurately.
According to a second aspect of the present invention, when the core numbers of the respective cores of the multi-core optical fiber are verified, the power of each of the optical signals put into and emitted from the multi-core optical fiber is measured thereby to measure the transmission loss of the multi-core optical fiber. It is therefore possible to confirm the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof and to measure the transmission loss of the optical fiber as its basic characteristic in one step simply, quickly and accurately.
According to a third aspect of the present invention, there is provided a multi-core optical fiber inspecting apparatus, in which the multi-core optical fiber having the plurality of cores arranged in one plane, comprising: the light source having the plurality of optical output terminals which are connected to the incident ends of the respective cores of the multi-core optical fiber and used for putting optical signals into the respective cores thereof; the optical signal taking means for taking out the optical signal emitted from the emission end of each core of the multi-core optical fiber in the time series mode according to the alignment order of emission-side cores of the multi-core optical fiber; the optical signal detecting means for detecting the optical signal thus taken out by the optical signal taking means; and the signal processing means for verifying core numbers of the respective cores of the multi-core optical fiber on the basis of the signal patterns of detection outputs of the optical signal detecting means. Therefore, the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof can be confirmed simply, quickly and accurately.
According to a fourth aspect of the present invention, in the multi-core optical fiber inspecting apparatus of the third aspect of the present invention, the optical signal taking means has the rotary plate formed with the opening of a size large enough to totally let pass all the optical signals emitted from the respective cores of the multi-core optical fiber, and the optical signal detecting means includes the light receiving element having an area large enough to collectively receive all the optical signals emitted from the respective cores of the multi-core optical fiber. It is therefore possible to confirm the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof and to measure the transmission loss of the optical fiber as its basic characteristic in one step simply, quickly and accurately.
According to a fifth aspect of the present invention, there is provided a multi-core optical fiber inspecting apparatus, in which the multi-core optical fiber having the plurality of cores arranged in one plane, comprising: the multi-output light source unit having the plurality of optical output terminals which are connected to the incident ends of the respective cores of the multi-core optical fiber and used for putting optical signals into the respective cores thereof; the rotary plate having at least one slit which is driven to rotate in such a way as to cross the optical beam emitted from the emission end of each core of the multi-core optical fiber; the optical signal detecting means for detecting the optical signal emitted from the emission end of each core of the multi-core optical fiber as the time series signal according to the alignment order of emission-side cores of the multi-core optical fiber; and the signal processing means for verifying core numbers of the respective cores of the multi-core optical fiber on the basis of the signal patterns of the time series signals emitted by the optical signal detecting means. Therefore, the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof can be confirmed simply, quickly and accurately.
According to a sixth aspect of the present invention, in the multi-core optical fiber inspecting apparatus of the fifth aspect of the present invention, the rotary plate has the opening other than the slit, the opening being large enough to let pass the optical beam outputs of all the cores of the multi-core optical fiber; the optical signal detecting means includes the large-diameter optical sensor capable of receiving the optical beam outputs of all the cores of the multi-core optical fiber; and the signal processing means obtains the transmission loss of the multi-core optical fiber on the basis of detection outputs of the optical sensor that has received the optical beam outputs of the multi-core optical fiber that have passed through the opening of the rotary plate. It is therefore possible to confirm the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof and to measure the transmission loss of the optical fiber as its basic characteristic in one step simply, quickly and accurately.
According to a seventh aspect of the present invention, as the signal processing means verifies the core number by measuring the time required until the slit passes the front of the emission end of each core of the multi-core optical fiber whose core number is to be verified after the slit passes through the optical path formed by the photocoupler, the core-to-core positional relationship of the multi-core optical fiber is determined with the position of the photocoupler thus disposed as a reference. Then there is sequentially created a condition in which the optical signal is produced in the time series mode from only the target core in order to verify its core number by measuring the time required until the slit passes the front of the emission end of the target core of the multi-core optical fiber 30 after it passes through the optical path formed by the photocoupler. Thus, the core number can be verified simply, quickly and accurately.
According to an eighth aspect of the present invention, in the multi-core optical fiber inspecting apparatus described in either the fifth or sixth aspect of the present invention, the multi-output light source unit is so arranged as to be able to control the level of the optical output put into each core of the multi-core optical fiber and to cut off only the optical output put into the core of the multi-core optical fiber whose core number is targeted for verification, and the signal processing means verifies the core number of the multi-core optical fiber on the basis of the signal pattern of the time series signal detected by the optical signal detecting means when the slit of the rotary plate passes the front of the emission end of each core of the multi-core optical fiber. Therefore, the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof can be confirmed simply, quickly and accurately.
According to a ninth aspect of the present invention, in the multi-core optical fiber inspecting apparatus described in either the fifth or sixth aspect of the present invention, the multi-output light source unit is so arranged as to be able to control the level of the optical output put into each core of the multi-core optical fiber and to increase or decrease only the optical output put into the core of the multi-core optical fiber whose core number is targeted for verification; the optical signal detecting means including: the photodiode for detecting the optical signal emitted from the emission end of each core of the multi-core optical fiber; the current-voltage converter circuit for converting the output current of the photodiode into a voltage signal; and two of the first and second comparator different in the reference voltage with the output signal of the current-voltage converter circuit as an input; the output condition of the first comparator is set as a condition for detecting the optical signals supplied from all the cores of the multi-core optical fiber; the output condition of the second comparator is set as a condition for detecting only the optical signal supplied from the core of the multi-core optical fiber whose core number is targeted for verification, and the signal processing means verifies the core number of the multi-core optical fiber on the basis of the outputs of the first and second comparators. Therefore, the coincidence between the alignment order of the input-side cores of the multi-core optical fiber and the alignment order of the output-side cores thereof can be confirmed simply, quickly and accurately.
According to a tenth aspect of the present invention, there is provided a multi-core optical fiber core-number verifying apparatus comprising:
a multi-output light source unit having a plurality of output terminals for use in putting optical signals from one end sides of the output terminals into the respective cores of a multi-core optical fiber;
light receiving means for detecting the optical signal emitted from the other end of each of the cores as an image; and
emission-position monitoring means which is connected to the light receiving means and capable of recognizing any core from which the optical signal has been detected by processing image data obtainable from the light receiving means.
With the arrangement above, as the optical signals produced from the other ends of the respective cores can collectively be recognized as an image in the multi-core optical fiber core-number verifying apparatus, the work of verifying the output cores of the multi-core optical fiber separately becomes unnecessary.
According to an eleventh aspect of the present invention, there is provided a multi-core optical fiber core-number verifying apparatus of the tenth aspect of the present invention, wherein
an infrared beam is used for the optical signal and that
an infrared camera is used to form the light receiving means.
According to a twelfth aspect of the present invention, there is provided a multi-core optical fiber core-number verifying apparatus according to the tenth aspect of the present invention, wherein
an infrared beam is used for the optical signal and that
the light receiving means includes an infrared sensor plate for converting the infrared beam into visible light, and a camera for photographing the infrared sensor plate.
With the arrangements above, the utilization of infrared beams allows distinguishing between the cores clearly without any influence of external light in those aforementioned multi-core optical fiber core-number verifying apparatus.
According to the thirteenth aspect of the present invention, there is provided a multi-core optical fiber core-number verifying apparatus according to any one of the tenth to twelfth aspects of the present invention, wherein
the multi-output light source unit includes at least one light source, and
a light switching device capable of converting the output light of the light source into a plurality of output light beams.
According to a fourteenth aspect of the present invention, there is provided a multi-core optical fiber core-number verifying apparatus according to any one of the tenth to twelfth aspects of the present invention, wherein
the multi-output light source unit has a plurality of light sources each capable of producing one output light beam.
With the arrangements above, putting the optical signals selectively into the respective cores of the multi-core optical fiber can be carried out easily and quickly in those aforementioned multi-core optical fiber core-number verifying apparatus.
According to a fifteenth aspect of the present invention, there is provided a multi-core optical fiber core-number verifying apparatus according to any one of the tenth to fourteenth aspects of the present invention, comprising:
input switching means which is connected to the multi-output light source unit and capable of controlling the multi-output light source unit as to switching cores to be fed with an optical signal, and
core coincidence decision means which is connected to the input switching means and the emission-position monitoring means and used to decide whether or not the core targeted by the input switching means as what is fed with an optical signal coincides with the core from which an optical signal output has been detected by the emission-position monitoring means.
With the arrangement above, the work of confirming the coincidence between the alignment order of input cores and the alignment order of output cores can automatically be carried out in the multi-core optical fiber core-number verifying apparatus.